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Pathogens
Antimicrobials
This guide DOES NOT APPLY to immunocompromised patients, facial cellulitis originating from dental infections, cellulitis associated with potentially contaminated wounds (including animal or human bites), or when cellulitis is associated with fresh or salt water exposure, where the pathogens are possibly different.
Cellulitis is an inflammation of the dermis and subcutaneous soft tissue. This is in contrast to impetigo which is an inflammation of the epidermis or superficial part of the skin. Impetigo is not very tender and usually responds to topical antimicrobials.
Characteristics of cellulitis are pain, swelling, erythema and warmth. Cellulitis can be non-purulent or purulent (abscesses) (See below).
If patient is very ill (febrile, toxic, hypotensive or has multiple sites), or experiences pain out of proportion compared to skin findings, consider necrotizing fasciitis or a deeper infection involving muscles or fascia.
Differential Diagnosis
Erythema migrans (Lyme Disease) is usually large (>5cm), has a much slower onset and not tender (though can be mildly pruritic).
If response to antibiotics is suboptimal, also consider herpes (vesicles or shallow ulcers). If pruritic, consider insect bites or urticaria.
Other less common causes may be associated with exposure to water (Aeromonas or Vibrio).
Non-purulent cellulitis
Purulent Cellulitis
